This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. ABSTRACT: Karolyn Buttle is supported by the grant, in part, to train users on the HVEM. She is supervised by M. Marko, and is kept abreast of the latest technical information on the HVEM operation by D. Barnard. During HVEM training sessions. K. Buttle sits with the user, and gives instructions on how to tilt the specimen, use the TV system for focusing, take pictures, etc. She is then responsible for assisting the user should any problems arise, and for changing specimens and developing negatives. In collaboration with M. Marko, she helps the user decide the best thickness and stain to use for the project, and gives advice on further work that might involve use of Sterecon or tomography. In many cases, K. Buttle also trains the user in thick-section techniques, and in how to stain sections for HVEM. In addition to her teaching/training responsibilities, K. Buttle is also responsible for HVEM user correspondence and for our mailed in grid screening service.